The Serious Fraud Office has begun an investigation into Wellington fund manager David Ross and his firm Ross Asset Management after court-appointed receivers found records for just $10.2 million of the $449.6 million he purportedly managed.

The SFO has been working with the Financial Markets Authority, which began its own investigation on October 25 and has since obtained a freeze on Ross's assets. John Fisk and David Bridgman of PricewaterhouseCoopers were appointed receivers and managers and have recommended all of the Ross-related entities be placed in liquidation.

"An evaluation of the information now available has concluded that there are reasonable grounds to believe that an offence of serious fraud may have been committed," said acting SFO chief executive Simon McArley.

"The SFO notes with concern the comments made by Mr Fisk that it is likely the historical returns advised to investors may be fictitious and that what has occurred has the characteristics of a Ponzi scheme," McArley said.

"Given the scale of the potential loss this is a matter we take extremely seriously."

David Ross has been hospitalised since the FMA raid on his premises.

Ross, formerly a share broker, managed funds on behalf of 900 privately wealthy individuals, with management fees averaging $4.4 million a year paid in each of the last three years.

The PwC investigation found inadequate record-keeping and has been unable to source much of the documentary evidence for trading and investment holdings that it needs to complete a full picture of what looks to have the characteristics of a Ponzi-style scheme, where investors were paid out at least in part using other investors' funds.

The Ross group's database purports to show investments worth $449.6 million, of which $152.4 million is said to be held in Australian investments, another $136.1 million in Canada, some $156.4 million in the US, $3.8 million in New Zealand, and $943,332 elsewhere. Of this, some $437.6 million was held by a Ross group subsidiary, Bevis Marks.

However, assets worth just $10.2 million, and $200,000 in cash deposits, had been identified in the receivers' initial searches, which they described as a matter of "considerable concern.'